Trigger repository mirror update via webhook

I configured Repository mirroring to mirror a github located repository, which is synced every now and then as described in https://docs.gitlab.com/ee/workflow/repository_mirroring.html. Due to this my gitlab-based-pipeline builds often only start with some delay, after pushing a change to github.

I would like to have a webhook, s.t. github can trigger the mirroring update on gitlab.